The overall objective of this research is to investigate the biological activity of endogenous virus-related genes of uninfected avian cells. We are particularly interested in studying normal cell genes that are related to the transforming genes of avian retroviruses. Transformation of NIH 3T3 cells by fragments of normal chicken cell DNA has been used to identify endogenous transforming genes of normal chicken cells. These genes will be further studied by molecular cloning and their relationship to retrovirus genes will be invesigated. The transforming activity of the endogenous sarc gene of normal chicken cells will be investigated by transfection assays of molecular clones containing endogenous sarc DNA.